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    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
 
    var arr = [100, 26, 18, 89,90]; //2,4,10,18
    arr.sort(function (a,b){
        return a-b
    })
  
    var n =0
    var arr1 =[]
    for(var i=0;i<arr.length;i++)
    {
        if(arr[i]<60)
        {
            arr1.push(arr[i])
        }
    }
    // document.write("不及格人数:" + arr1.length)
    var arr3 = ["唱歌","跳舞","弹琴","脱口秀","唱歌","跳舞"]
    var arr4=[]
    for(var i=0;i<arr3.length;i++)
    {
        if(arr4.indexOf(arr3[i])==-1)
        {
            arr4.push(arr3[i])
        }
    }
    document.write(arr4)


    </script>
</body>
</html>